The mechanism underlying the NK cell activity is explored in vivo and in vitro using genetical analysis in combination with inducers or inhibitors or NK activity. Pigment mutations will in particular be analyzed in relation to lysosomal function and NK function. The target structures for NK cells are being analyzed a) across versus within the species and b) using differentiation inducing agents as NK susceptible targets do frequently become NK resistant upon differentiation. The regulation of NK function in relation to age and tissue distribution will be studied using agents known to occur at increased or decreased concentrations at periods when NK functions are significantly changed from normal values. Experiments will be performed to further analyze the possible function of NK cells in vivo with regard to oncogenesis and resistance to tumor outgrowth. NK susceptibility of in vivo growing primary tumors will be studied in relation to attempt to treat such tumors with various immunoregulatory agents such as interferon.